SwiftAutoLayout
SwiftAutoLayout is a tiny DSL for Autolayout intended to provide a more declarative way to express layout constraints. Here's a quick example:
// this:
let constraint = view1.left == view2.right * 2.0 + 10.0 ~ 750
// is equivalent to:
let constraint = NSLayoutConstraint(item: view1, attribute: NSLayoutAttribute.Left, relatedBy: NSLayoutRelation.Equal, toItem: view2, attribute: NSLayoutAttribute.Right, multiplier: 2.0, constant: 10.0)
constraint.priority = 750
You may notice that this looks a lot like the linear equation that a constraint represents. From the Apple documentation:
The relationship involves a first attribute, a relationship type, and a modified second value formed by multiplying an attribute by a constant factor and then adding another constant factor to it. In other words, constraints look very much like linear equations of the following form:
attribute1 == multiplier × attribute2 + constant
SwiftAutoLayout allows you to more effectively communicate the intent of a constraint by making the syntax more similar to the equation that it represents.
Installing
Use Swift Package Manager or add SwiftAutoLayout.xcodeproj as a subproject and link against either SwiftAutoLayout-iOS.framework or SwiftAutoLayout-Mac.framework depending on the platform.
Attributes
Layout attributes are defined as properties added in extensions of UIView and UILayoutGuide on iOS and NSView and NSLayoutGuide on OS X. For example, UIView.width and UIView.height represent NSLayoutAttribute.Width and NSLayoutAttribute.Height, respectively.
Layout guides (conforming to UILayoutSupport) in UIViewController are also supported using the topLayoutGuideTop, topLayoutGuideBottom, bottomLayoutGuideTop, and bottomLayoutGuideBottom properties.
Relations
Relations are expressed using the overloaded operators == (NSLayoutRelation.Equal), >= (NSLayoutRelation.GreaterThanOrEqual), and <= (NSLayoutRelation.LessThanOrEqual).
Examples
Activating Single Constraint
(view1.left == view2.right * 2.0 + 10.0 ~ 750).active = true
Activating Multiple Constraints
NSLayoutConstraint.activateConstraints([
view2.centerX == view2.superview!.centerX,
view2.centerY == view2.superview!.centerY,
view1.left == view2.right * 2.0 + 10.0 ~ 750,
view1.top == view2.bottom + 5.0,
view1.width >= 200,
view1.height >= 400,
view1.trailing == layoutGuide.trailing,
view2.leading == layoutGuide.leading
])
Contact
- Indragie Karunaratne
- @indragie
- http://indragie.com
License
SwiftAutoLayout is licensed under the MIT License.
19.1k Jan 2, 2023
45 Jun 28, 2022
0 Nov 28, 2021
104 Dec 28, 2022
7.3k Jan 4, 2023
90 Sep 1, 2022
83 Jan 29, 2022
57 Nov 21, 2022
27 Jul 25, 2022
53 Mar 31, 2022
3 Nov 8, 2022
3.3k Jan 6, 2023
171 Oct 11, 2022
25 Feb 20, 2022
36 Jul 15, 2022
155 Dec 10, 2022
1 Oct 29, 2021
79 May 25, 2022